1. Field of the Invention
The present invention relates to a motor device preferably for use in, e.g., a blower installed in a duct and, more particularly, to a motor device configured to drive a motor to maintain an air quantity or a flow rate at a constant value.
2. Description of the Related Art
In the related art, a blower is extensively used in different fields. For example, in a ceiling-embedded ventilation system, an indoor air is ventilated by a blower through a duct. In this ventilation system, the load of the blower is changed by the contamination of the duct or the contamination of a filter installed within the duct. International Publication Nos. 2007/040180 and 2009/110219 disclose a configuration in which the fluctuation of a flow rate (or an air quantity) attributable to the change in load is suppressed by calculating an air quantity from a rotation speed of a motor and a driving current and controlling the operation of the motor based on the air quantity thus calculated. Japanese Patent Application Publication No. 2008-43083 discloses a configuration in which a motor is driven by detecting a rotation position of a rotor using a driving current without additionally installing a sensor for detecting a rotation position of a rotor (in a so-called sensorless manner).
With regard to the control of the motor for the blower or the like, Japanese Patent No. 3653670 discloses a configuration in which a motor is controlled by what is called vector control.
When driving the motor for the blower or the like, it would be convenient if the motor can be driven by a process simpler than those in the related arts such that the flow rate is kept constant.